Sound signaling apparatus



n. c. CLEMENT 2,452,571

SOUND SIGNALINGAPPARATUS A 2 Sheets-Sheet x Nov. 2, 1948.`

Filed June 14, 193s INVENTOR.

ATTORNE i l l lll -i I l |||l L T I I lI ILL y !l Eig!! i n L r@ o e Q al. 2

l. c. CLEMENT f 2,452,571

SIGNA I Nov. 2,1948.

' l SOUND LING APPARATUS 2 Sheets-Sheet 2,

Filed June 14, 1933 INVENTOR.

/van C C/e/lenf B* Many Patented Nov. 2, 1948 SOUND SIGNALING APPARATUSo Ivan C. Clement, Wakefield, Mass., assignor, by

mesne assignments, to Submarine Signal Company, Boston, Mass., aciirporation of Delaware Application June 14, 1933, Serial No. 675,700

9 Claims.

The present invention relates to an apparatus for transmitting andreceiving submarine or subaqueous signals, and .more particularly to theuse of compressional waves in a frequency range above or near the upperlimit of audibility o f the human ear.

The invention further relates to the transmission of a directive beam ofcompressional waves with the use of piezo-electric crystals which may bequartz but preferably are Rochelle-salt crystais or crystals Vhavingsimilar piezo-electric properties.

In the present invention crystals of the Ro-.

chello-salt type are'not used purely as a so-called compressionalcrystal in" which a compression between two faces of the crystal sets upan electrical potential in aV direction parallel to the faces and normalto the opposite faces but the crystals are used as bending crystals, andin this 4connection the method of support and the method of applying thevibratory energy'to the crystal are substantially different. Thecrystals as indicated may be used individually or they may be mounted ingroups in face-to-face relation, the outer .electrodes being connectedtogether and serving as one pair of electrodes while the innerface-to-face'electrodes serve as the common electrode.

1'lhe device of the present application may-in particular be used toreceive supersonic waves within a broad range of Vfrequencies by the useof a plurality of crystals substantially aligned in the same planecovering a large surface as compared with the wave lengthl of the wavewhich ls.

moved; Fig. 2 shows a sectional view along the line 2-2 of 1; Fig. 3shows a perspective view of the arrangement of the crystals; Fig. 4shows a detail view`of the application of the electrodes to thecrystals; Fig. 5 shows a plan rview ofthe modification of the systemshown in Fig. l; Fig. 6 shows a part sectional view of the samemodification corresponding to Fig. 2; Fig. 'l shows a detail of themethod of the support of the crystals as used in Fig. 5; and Fig. 8shows 2 a modification of the detail of the crystal as shown -in Fig. 4.y

In Figs. 1 and 2 the apparatus is contained in a casing I which issupported preferably by the center piece 2 at the bottom of the middleof the casing. As illustrated in Figs. 1 and 2 the support may becircular so thatthe whole device may be mounted in a bearing and.rotated about a vertical axis. The casing I, which may be of metal, isprovided with a heavy back plate 3 which tapers somewhat to the top ofthe apparatus as shown more particularly in Fig. 2. Within the backplate 3 is a recessed portion 4 in which the elements 5, E, 1 and 8 arepositioned. r.These elements, as illustrated in Fig. 3, may be molded orformed to have recessed portions 9, I0, II. etc., in which the crystalsmay be positioned. The molded elements 5, 6, 1 and 8 are spaced apart inparallel relation and form pockets in which the ends of the crystals I2,I3, I4, etc., rest. This is shown quite clearly in Fig. 3 where one endof the crystal I2 rests in the pocket 9 formed in the support 6 whilethe other end of the crystal rests in a corresponding pocket in thesupport l.

Each crystal is provided with electrodes at both sides thereof. Theseelectrodes are indicated in Fig. 4 by numerals I5 and I6, and, as `shownin Fig. 3, each electrode is conductively connected to a conductor Ilconnecting to a main conductor I8, the conductor I'I resting in a grooveparallel to the supporting element while the conductor I8 connects allthe conductors I1 in the cross grooves together. The crystals may all beconnected inparallel with the top electrodes all connected together tothe same conductor and the lower electrodes connected together to adifferent conductor or any parallel series combination may be employed.

The supporting elements 5, 6, 'I and 8 may be of any yielding materialsuch as rubber but 1 prefer to use'the substance which is known asglyptal and which is a synthetic rubber but possesses the desirablequality that it is yielding but has slight elasticity. At the front ofthe crystals thereris positioned a rubber diaphragm I 9 the surface ofwhich preferably comes in con'- tact with the crystal itself. While thediaphragm I9 may have a substantial thickness it is preferable to haveit of such a material and thickness that the compressional waves aretransmitted through it as part of the propagating medium so that it doesnot act in eiect like a diaphragm and produce reflections at itssurfaces. For this purpose soft rubber is preferably used which hasabout the same sound hardness as water and on account of which thecompressional'waves are transmitted through it as though it were a partof the propagating medium itself.

The diaphragm i9 may be held in place by the clamping ring 2) suitablybolted to the back casing through the bolts 2i, 2l arranged around theperiphery of the casing. The diaphragm i9 may have a thick centralportion and be provided with a thin neck portion 22 in which a hardfiber ring 23 may beinserted for the purpose of furnishing a rm clampingsurface and preventing yielding in the clamping joint.

In the operation of the device shown in Figs. 1 to d, inclusive, thesound impressed upon the diaphragm I9 is transmitted directly to thecrystals causing a bending of the crystals between the two supportingends. This bending creates a potential difference between the faces ofthe crystals which is detected in the receiver or receiving circuit.When the device is used as a transmitter, electrical energy is appliedto the electrodes of the crystal and the crystals are made to bend'inthe same manner that they are bent when excited by compressional waves.

The open spaces'fi and 25 between the crystal supports may, ifdesirable, be partially or substantially filled with some fluid orliquid in which the crystals will not dissolve. Substances like castoroil or other suitable oils may be used for this purpose.

In the modifications shown in Figs. 5, 6, 'l and 8 the crystal 25 issupported by rubber corners 26, 2 and 28 in which the corners of thecrystals nt with the attached electrodesg and 39. The electrode 39, asindicated, may be connected to conductor 3 l, the electrode 30 to theconductor 32.

The corners .26, 2l and 28, supporting three corners of the crystal, maybe made of molded rubber or of the substance'of the nature previouslydescribed. The crystals with the molded corners attached are held inposition in the casing i by means of the plate 33 which is supported ona shoulder 3d in the casing by means of the bolts 35. The plate 33 isperforated at points corresponding to the free corners of the crystals,and through these perforations the rods 36, 3l, 38, etc., operate,transmitting acoustic vibrations to the free corners of the crystals.The rods themselves may be of rubber or other` similar molded materialor they may be metallic and the diaphragm 39 itself rubber. In themodification illustrated in these figures the same type of bendingaction is obtained as that described in connection with the operation ofthe first modification of the invention. It will be noted that in bothmodifications the crystals are substantially placed in the same plane,and the front surface or face of the crystals substantially lies in thisplane. With this arrangement the sound energy approaching normal to thesurface of the diaphragm excites all of the crystals in the same phasewhile the sound energy approaching from any' but the normal directionexcites the crystals out ofphase. In this Way it will be readilyobserved that the device is highly directional in a direction normal tothe surface of the diaphragm.

In Fig. 8 a slightly dierent form of crystal structure is shown. In thisfigure it will be noted that two similar crystals are mounted infaceto-face contact. The crystals in this figure are mounted so that thesame polarity is produced on the top and bottom electrodes of thecombination, with the other polarity on the adjacent or common electrodebetween the two crystals.

d 'I he crystal structure illustrated in Fig. 8 may be substituted forthat shown in Figs. 2 and 5 and the crystals will substantially operateand act in the same Way.

Having now described my invention. I claim:

1. A submarine transceiver including a plurality of individualPiezo-electric crystals of the Rochelle salt type formed as flat plates,means positioning said crystals with similar surfaces in the same planeand supporting the crystals only near their-end portions, a diaphragmcovering the front of the crystals and in acoustic relation thereto,said crystals being provided with electrodes and means conductivelyconnecting said electrodes together.

2. A submarine transceiver including a piezoelectric crystal oftheRochelle salt type formed as a flat plate, means supporting the platenear its end positions on one side, a diaphragm covering the plate onthe other side and in acoustic relation thereto, said crystal beingprovided with electrodes and means conductively connected to saidelectrodes.

3. A submarine transceiver including a casing having a heavy back frame,a plurality of supports which permit limited flexure mounted within thecasing at the back, a plurality of piezo-electric crystals of theRochelle salt type positioned with their end portions only on saidsupports and a yielding diaphragm covering the front of said crystalsand in acoustic relation thereto.

4. A submarine transceiver including a casing having a rigid backelement, a flat plate of glyptal mounted on said back element, saidplate being formed with regularly spaced pockets, piezo-electriccrystals of the Rochelle salt type positioned with their ends in saidpockets and means for acoustically independently connecting saidcrystals with the compressional wave propagating medium.

5. A submarine transceiver including a casing having a rigid backelement, a plurality of piezoelectric crystals of the Rochelle salttype, means for mounting said crystals individually in said casing andsupporting said crystals at their back faces only near their endportions, and means in contact with said crystals on their front facesat the front of said casing for acoustically independently connectingsaid crystals with the compressional wave propagating medium.

6. A submarine transceiver including a casing having a rigid backelement, a plurality of piezoelectric crystals of the Rochelle salt typeadapted to be operated through the bending-of the same, means mountingsaid crystals and supporting the same at their back faces near their endportions, means connecting said crystals acoustically at their frontfaces with the propagating medium for exerting individual pressure onthe unsupported part of each of said crystals. Y

7. A submarine transceiver including a casing having a rigid backelement, a plurality of piezoelectric crystals of the Rochelle salttype, means for mounting said crystals in said casing with similarsurfaces inv substantially the same plane and supporting the same atleast at two places thereon on their back faces, means acousticallyconnecting said crystals at their front faces individually with thepropagating medium, exerting pressure at places on the crystals otherthan the supporting places.

8. A submarine transceiver comprising a casing having a rigid backelement,V vajplurality of piezo-electric crystals, means for mountingsaid crystals on the back of the said casing in substantially the sameor parallel planes, supporting the same at some of the corners thereofsymmetrically with a center line across the face oi' the crystal andmeans acoustically connecting said crystals to the propagating medium toexert acoustic vibrations on said symmetrical line normal .to the faceof the crystals.

9. A submarine transceiver comprising a casing having a rigid backelement, a plurality of piezo-electric crystals,` means for mountingsaid crystals onthe back of the said casing in substantially the same orparallel planes, said means including corner elements placed symmetricalwith a center line across the face of the crystals for holding saidcrystals and means holding said corner elements in place, and meansacoustically connecting said crystals to the propagating mediu'm toexert acoustic vibrations on said crystals normal to the face of thecrystals on the unsupported corners thereof on a point on said centerline.

IVAN C. CLEMENT.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,002,567 Davison Sept. 5, 19111,380,981 Langmuir June 7, 1921 1,619,854 Crossley Mar. 8, 19271,624,357 Nicolson Apr. 12, 1937 1,655,625 Nicolson Jan. 10, 19281,688,694 Ellis Oct. 23, 1938 1,802,782 Sawyer Apr. 28, 1931 1,860,529Cady May 31, 1932 1,866,267 Nicolson July 5, 1932 ,2,045,430 NicholidesJune 23, 1936 FOREIGN PATENTS Number Country Date 145,691 y GreatBritain July 28, 1931 301,034 Great Britain Apr. 16, 1929 309,276 GreatBritain Apr. 11, 1929 613,799 France Sept. 4, 1926

